PHY 120 study problem

label Physics
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The tub within a washer goes into its spin cycle, starting from rest and reaching an angular speed of 14 rad/s in 8.5 s. At this point, the lid is opened, and a safety switch turns off the washer. The tub slows to rest in 13.5 s. Through how many revolutions does the tub turn? Assume constant angular acceleration while the machine is starting and stopping. Answer in units of rev.

Jun 23rd, 2015

Assuming constant angular acceleration while it is starting and stopping.

SPEED UP

Velocity (vi) = 0 rev/s

Velocity (vf) = 14 rev/s

Time (t) = 8.5s

Δx = 1/2 ( vi + vf ) * Δt

Δx = 1/2 ( 0 + 14 ) * 8.5

Δx = 59.5 rev

SLOW DOWN

Velocity (vi) = 14 rev/s

Velocity (vf) = 0 rev/s

Time (t) = 13.5s

Δx = 1/2 ( vi + vf ) * Δt

Δx = 1/2 ( 0 + 14 ) * 13.5

Δx = 94.5 rev

Total revolutions in 22 seconds:=133.6+57.6=154rev

Jun 23rd, 2015

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Jun 23rd, 2015
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Jun 23rd, 2015
Sep 26th, 2017
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